1. Field
The following description relates to optical communication systems, and more particularly, to multi-lane signal transmitting and receiving apparatuses.
2. Description of the Related Art
ITU-T G.709 defines a virtual concatenation standard (VCAT) for an optical transport network (OTN) in an inverse multiplexing scheme capable of transmitting a high-capacity OTN signal in the form of several low-capacity OTN signals. For example, the VCAT standard for the OTN uses a scheme of dividing one 40 Gbps data signal into four 10 Gbps data signals and transmitting the 10 Gbps data signals, in which the four signals are transmitted with different delays because a physical line for each 10 Gbps data signal has a different length. The delay difference among the signals is called a skew. FAS and multi-frame alignment sequence (MFAS) signals are used in each 10 Gbps data signal to overcome a skew among the four signals. A receiving stage compares MFASs of four data signals aligned through the FAS byte and calculates delay amounts of the signals. The calculated delay amounts are used to compensate for the skew of the four signals.
FIG. 1 illustrates an apparatus for transmitting a 100 Gbps Ethernet signal (100 GbE) conforming to a VCAT standard for an OTN in the form of eleven 10 Gbps optical channel transport unit (OTU) 2 signals. An actual data rate of 100 GbE is 103.125 Gb/s±100 ppm, and data capacity of optical channel payload unit (OPU)2 in which an actual client signal of OTU2 is contained is 9.995276962 Gb/s (=238/237×9.95328 Gb/s). Since data capacity is 99.952769 Gb/s (=10×9.995276962 Gb/s) when ten OPU2 signals are simply inverse multiplexed, it is insufficient to contain the 100 GbE signal bit-transparently. Accordingly, the 100 GbE signal can be bit-transparently sent through eleven OTU2 signals, as in FIG. 1.
However, in case of OTU2-11v in which eleven OTU2 signals are inverse multiplexed, total data capacity is 109.948046582 (=11×238/237×9.95328 Gb/s). Accordingly, only about 93.794% of the total data capacity is used to contain 100 GbE and 6.823 Gb/s is not used. This structure is inefficient.
Another example in which a 160 Gbps signal is transmitted will now be described. Methods using a conventional standard frame to transmit a 160 G signal include OTU1-64v, OTU2-16v and OTU3-4v methods. Among them, OTU3-4v is capable of designing low-power chips with the lowest capacity. However, since OTU3-4v employs four virtual containers, transmission only through four lines or wavelengths can be achieved. That is, since sixteen 10 G optic modules are initially cheaper than four expensive 40 G optic modules, OTU2-16v is preferred over OTU3-4v. However, when the four 40 G optic modules become cheaper in the future, OTU3-4v will be used. That is, demapping and mapping must be unnecessarily performed in order to convert a signal using OTU2-16v or OTU3-4v according to optic modules in use.
Also, when an OTU3-4v line card using four 40 G optic modules, which will be cheap in the future, is implemented, the following must be considered. For electric interface between a 40 G optic module and a framer, it is very difficult and costly to connect them at a serial 40 Gbps rate. Since a high-speed 40 Gbps signal suffers from relatively severer attenuation, a transmission distance becomes shorter. Accordingly, interfacing through parallel data at a relatively lower rate is required. In case of interfacing through gigabit parallel data, a skew problem among parallel data arises. Thus, interfacing through parallel data requires a separate apparatus for compensating for a skew among the parallel data.
Another example in which a 40 Gbps signal is transmitted will now be described. In case of a 300 pin 40 G optical transponder standardized in the multi-source agreement (MSA), an interface to a framer has 16×2.5 Gbps. Also, a deskew channel of 2.5 Gb/s equal to a parallel data rate must be separately used to compensate for a skew between 2.5 G parallel data. Since this deskew channel has been defined to interface parallel data of 16 channels, it is not compatible with other interface standards. In addition, an optic module interface for a 40 G Ethernet signal, which is being standardized, has a 4×10 Gbps interface that has no separate deskew channel. Accordingly, when a transmission framer and a 40 G Ethernet optic module are interfaced, it is necessary to compensate for a skew between high-speed gigabit parallel data signals without a deskew channel. That is, a resultant structure is inefficient since different deskew structures are required for a 16×2.5 Gbps+skew channel compensation interface and a 4×10 Gbps interface in order to support each optic module.